1. Field of the Invention
This invention relates to a transmission type illumination optical microscope, and in particular, to an objective lens used in this microscope and a method of using the microscope.
2. Description of Related Art
FIG. 1 shows a schematic structure of an example of a conventional transmission type illumination optical microscope. In this figure, reference numeral 21 represents an eyepiece; 22, a lens barrel; 23, a microscope frame; 24, revolver attached to the lower portion of the lens barrel 22 through the microscorpe frame 23; 25, an objection lens mounted to the revolver 24; 26, a stage supporting section attached to the microscope frame 23 so that it can be raised and lowered; 27, a lower stage retained on the stage supporting section 26 so that it can be moved along an X axis (or a Y axis) with respect to the stage supporting section 26; 28, an upper stage retained on the lower stage 27 so that it can be moved in a direction perpendicular to the lower stage 27, that is, along the Y axis (or the X axis) with respect to the stage supporting section 26; 29, a surface illuminant fitted into the upper stage 28 with respect to the lower stage 27; 32, a lower stage control knob for moving the lower stage 27, together with the upper stage 28, with respect to the stage supporting section 26, and 33, a focusing knob for raising and lowering the stage supporting section 26 through the microscope frame 23.
The lower stage 27 and the upper stage 28 constitute a microscope stage. The specimen 30 is placed on the surface illuminant 29 through hard glass or sapphire glass and is held on the stage by a well-known clamp, not shown. Focusing is performed by turning the focusing knob 33, and when the stage control knob 31 or 32 is turned, the specimen 30 is moved in the X or Y direction. In this way, a desired observation is carried out.
Consider the case of cytodiagnosis in which such a transmission type illumination optical microscope is used. The specimen 30, as shown in FIG. 2, is made in such a away that cells of a sample are placed on a slide glass 30a (preparation) which is a sample holding member, and are covered with a glass cover 30b which is a protective transparent member, and thereby the sample is sealed between the sample holding member 30a and the protective transparent member 30b. In this case, the protective transparent member 30b usually has a thickness of 0.17 mm, and it is common practice that the objective lens 25 used is corrected for spherical aberration in accordance with this thickness of the protective transparent member 30b. For a dry objective lens which has a numerical aperture (NA) of 0.8 or more, in order to accommodate variations in thickness of the protective transparent member 30b, some of protective transparent members are designed so that spherical aberration can be corrected, ranging in thickness from 0.1 to 0.2 mm.
In recent years, high-speed and low-cost treatment in such cytodiagnosis and histodiagnosis has become necessary. Consequently, the high-speed preparation of the specimen 30 has also become necessary. This brings about the advent of an automatic sealing machine in which high-speed treatment of preparation of the specimen, namely sealing work of the sample, is realized (500-1000 pieces per hour). According to this machine, instead of the conventional glass cover used as the protective transparent member 30b, a transparent macromolecular film (0.1 mm in thickness), for example, like cellulose acetate, to which an adhesive sealant is applied, is used and pressed against the sample holding member on which the sample is placed, to thereby obtain a protective transparent member with a thickness of approximately 0.12 mm, including the layer thickness (0.02 mm) of the sealant. When this specimen is observed through a common objective lens such as that mentioned above, observation is carried out in a state where spherical aberration is not completely corrected, and thus there is the problem that the actual state of the sample cannot be correctly analyzed. In order to solve this problem, it is conceivable to use an objective lens in which the spherical aberration can be corrected with respect to a change in thickness of the protective transparent member, mentioned above. However, the objective lens of this type is very expensive and in addition, requires a manual operation for correction. Hence, the problem arises that not only does this cause in increase in treatment cost of cytodiagnosis or histodiagnosis, but it cannot completely meet the requirement for handling a large amount of specimens at a high speed.
It is, therefore, an object of the present invention to provide a microscope objective lens which allows favorable and easy observation of the sample of a specimen provided with a protective transparent member having a thickness in a predetermined range, including a specimen made by the automatic sealing machine, and to provide a microscope using this objective lens and a method of using the microscope. In order to achieve this object, the microscope objective lens according to the present invention is constructed with fixed lens units having a numerical aperture NA which is 0.6xe2x89xa6NAxe2x89xa60.8 and a magnification xcex2 which is 40xe2x89xa6xcex2xe2x89xa663, to observe a sample placed on the sample holding member and covered with the protective transparent member having a thickness t which is 0.1 mm less than t less than 0.15 mm. The microscope according to the present invention includes a stage for supporting a sample placed on the sample holding member and covered with the protective transparent member having the thickness t which is 0.1 mm less than t less than 0.15 mm; an objective lens constructed with fixed lens units having the numerical aperture NA which is 0.6xe2x89xa6NAxe2x89xa60.8 and the magnification xcex2 which is 40xe2x89xa6xcex2xe2x89xa663, to form a magnified image of the sample; and an eyepiece for observing the magnified image of the sample formed by the objective lens.
The method of using the microscope according to the present invention is to place the sample on the sample holding member and to cover the sample with the protective transparent member having the thickness t which is 0.1 mm less than t less than 0.15 mm so that it is observed through the protective transparent member, the objective lens constructed with the fixed lens units having the numerical aperture NA which is 0.6xe2x89xa6NAxe2x89xa60.8 and the magnification xcex2 which is 40xe2x89xa6xcex2xe2x89xa663, and the eyepiece.
This and other objects as well as features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments when taken in conjunction with the accompanying drawings.